How do I make sunlight emit between clouds?
This has been asked before many times.

You need volumetric lighting to see beams of light shining through the environment

The reason you would see those rays in the real world is because all the suspended particles in the air (smoke or mist) reflect some light, making the air not completely transparent anymore.

Volume scatter simulates that effect.

Add volume scattering as volume for the world (or create a big box that surrounds the scene and connect a volume scatter node to the volume of the material shader as shown on this post). The default value of 1 is way to high, so bring it down a bit.

Add a lamp and give it a very high value for intensity.

Create a plane with a texture that controls the transparency.



IF you want a more elaborate scene, then create clouds with the cloud generator add-on. The important part is that the clouds create different degrees of opacity between the light and the ground